It is proposed to study the sensitivity of membranes of photoreceptor outer segments to mechanical damage, heat, enzymes, detergents and other chemical agents by electron microscopy of membranes or freeze-fracture replicas of membranes. It is proposed to carry out chemical analyses for molecules of interest in specific retinal regions and to observe how light and dark adaptation influence these values. The molecules include taurine and other amino acids. It is further proposed to continue certain neuroanatomical studies on the retinas of the rhesus monkey and ground squirrel.